Heating of fluids



Nov. 2, 1943. QBERSTAD HEATING OF FLUIDS Filed April 25, 1942 I NVENTOR 0 n A N "m R R m E T m I 7, s m m w Patented Nov. z, 1943 UNITED STATES I PATENT OFFICE.

HEATING or r'nurns Irving oberstad, Chicago, 111., assignor to Uni-; 'versal Oil Products Company, Chicago, 111., a corporation of Delaware Application April 25.19% Serial no. 440,411

-4. Claims. 01. 122-356) This invention relates to the heating of fluids I and more particularly to a means for increasing the heating capacity of heaters of the so-called "double end fired type. The invention may be advantageously employed in the many existing heaters of this type as well as in new heater installations. y

In the petroleum industry there are at present a great many heaters of'thejype above mentioned being employed in various processes for the refining and conversion of crude oil to produce marketable products such as gasoline, naphthe, fuel oil and various lubricants. It can read ily b seen that any means for enlarging the output of these heaters will be beneficial to the industry.

The features of the present invention provide means for obtaining additional heating capacity without necessitating radical or expensive changes in existing heater structures. It is also possible in new heaters to employ this invention to provide higher heating capacities without increasing the overall size of the heater as compared to previously disclosed tube arrangements for this type of heater.

In heaters of the so-called "double end fired type it has been the general practice to install rows of radiant heating tubes along the floor and roof of the heater. It has also been common practice to install. rows of radiant heating tubes along the end walls above the burner ports. The cooler combustion gases are utilized to heat a bank of convection heating tubes which are generally disposed in a zone located between the two radiant heating zones of the heater.

In my invention I propose to install additional of theinvention more apparent reference is made to the accompanying diagrammatic drawing and the. following description thereof. In the drawing, i

Fig. l illustrates in sectional elevation a doubleend-fired heater embodying one form of the invention. 4

In Fig. 2 an alternate arrangementof the invention is shown. r

Referringto the drawing the heater comprises the end walls i, side walls not shown, the roof 2, and the fioor 3 which may be constructed of a suitable refractory material suchas fire clay,-

silica or highalumina brick or tile. The refractory walls and roof may be of any desired type of construction and the whole structure may be supported upon a'concret'e foundation 4.

Burner ports 51 are provided in opposite ends of the heater for the introduction of suitable fuels and regulated quantities of air. In the case here shown each burner 8 is-adapted for use with liquid fuel. The fuel is admitted to each burner through a valve 8 and conduit i and steam or air for atomization of the fuel is admitted through the valve sand conduit Hi. In the burner, passages are so arranged, that when steam is used it first heats the oil and then atomizes it so that it is readily ignited when mixed with the air introduced through the ports i2. Dampers, are 7 radiant heating tubes by suspending two substan- I 5 tially vertical rows of horizontally disposed tubes i from the roof of the heater at a point imme-- diately above the previously mentioned convection heating zone. In this way I add a substan tial amount of heating surface without increasing the size of the furnace structure. In addition these supplementary'tubes will have a higher heat input than the average of the other tubes of the heater since they are subject to superimposed radiant and convection heat. For this reason the increase in heating capacity realized will be more than proportional to the number of tubes added. This higher heat input to the additional tubes provided in the ports l2, for regulating the quantity of air admitted to the heater. I

Spaced from the end walls i are two bridge walls H wh ch extend from the floor upward-for a substantial distance and are spaced apart to providea fluid heating zone therebetween through which combustion gases fromzones ii pass before entering the. flue i5. Within the zone defined between the bridge walls are disposed a bank IQ of heating tubes which, because theywill be exposed to principally convection or fluid heat,

I will have a relatively low rate of heat input andtherefore are usually employed as preheating or initial heating tubes. Adjacent 'to the floor of the heater in combustion and radiant heating zones li a plurality of heating tubes II,- are -placed. Other radiant heating tubes I 8 and iii are disposed in will also make it possible to receive the benefits of increased heating capacity without a proportional increase in pumping costs due to pressure drop through the heater.

vIn order to make the features and advantages 7 zones I i adjacent the roof 2, and wall I, respectively. Since these tubes are subject to direct radiant heat on one side andrefiected radiant heaton the other side they have a much higher heat input than the tubes of bank "5. It is,

however, well within the scope of the invention 7 to omit the tubes i9 when desired. v

' In many existing heaters tubes have already my invention two rows of tubes 20 are disposed as shown above the. previously mentioned fluid heating tubes I8.

In the preferred. form of'the invention the tubes 20 are disposed in a staggered arrangement in order, that they. may be exposed to radiant heat on both sides. ment as shown in Fig. 2 the tubes are not staggered and therefore do not absorb as much heat as the tubes in the preferred arrangement but this is more or less equalized by the additional tubes it is possible to include when employing this method of disposition.

In Fig. 1 the various banks of tubes are shown connected for series flow therethrough, but it is also well within the scope of the invention to employ various othermethods of how. For example the incoming fluid stream. may be split into two portions each one of which may be passed in series through half of the tube l K andthereafter in series through the tubes ll along the floor of one of the combustion zones in the same combustion zone, thence through one row of the tubes 20, after which the two streams In the alternate arrange- I total for the 88 radiant heating tubes of 968,000.

invention; an additional heating capacity of 96,000 B. t. u. per unit of heater width will be realized or an increase of about 8%. This increase may be obtained with a heating surface increase of approximately 5.7%.

The phrase unit of heater width" as used in this specification refers to a heater width which willgive one square foot'of heating surface per tube where all tubes are the same size.

I claim as my invention: 7

1. In a heater of the class described having a pair of independently fired combustion zones and may be joined together and transferred to any additional equipment desired depending upon the process in whichthe heater is being em ployed.

In another variation of the invention two in"- dividual streams of fluid may be passed in a parallel flow arrangement through the heater, the heating conditions of each stream being regulated as desired by manipulation'of the firing conditions in the separate combustion zones.

As an illustration of its utility a comparison between the capacity of a heater without the invention and a heater employing the invention follows. 7 In the heater shown in Fig. 1 a total of 52 fluid heating tubes is employedalong with a total of 88 radiant heating tubes when the tubes 4 20 are not used. The fluid heating tubes have a rate of heat input of approximately 4500 B. t. u. per square foot of surface or for the 52 fluid heating tubes a total of 234,000 B.- t. u. per unit of heater width. The radiant heating tubes will have a heat input rate of about 11,000 B. t. u. per square foot of heating surface or a a centrally disposed convection zone receiving combustion gases from both combustion zones, a plurality of heating tubes disposed within said "convection zone, heating tubes disposed adjacent the floor of said combustion zones and heating tubes disposed adjacent the roof of saidcombustion zones; two substantially vertical rows oi horizontally disposed tubes disposed .above said convection zone, each of said rows being posi tioned in the direct path of hot combustion gases from at least one of said combustion zones.

2. In a heater of the class described having a pair of independently fired combustion zones and a centrally disposed convection zone receiving combustion gases from both combustion zones, a plurality of heating tubes disposed within said convection zone and heating tubes disposed adjacent' the floor, roof and one wall of each of said characterized in that said two substantially vertical rows of tubes are arranged in staggered formation.

4. A heater as described in claim 2 further characterized in that said two substantially vertical rowsof tubes are arranged in staggared iormation. I l 4 IRVING OBERSTAD. 

